1. Field of the Invention
This invention relates to examination of light in general as well as the examination of the spectral frequencies associated with various colors in the visible spectrum.
The serious study of colors began with the works of Newton who conducted most of his experiments with a narrow slit illuminated by sun light in combination with prisms and lenses. The resulting formation of the so-called natural spectrum of colors ranging from red through violet as found in the formation of rainbows was accepted as the starting point for the study of color. As far as Newton was concerned, there were seven colors which could be seen by the human eye and all seven colors could be reconverged to form natural light.
Subsequently, the investigation into color theory took a new turn when it was discovered that all colors in the visible spectrum could be derived from a certain few colors, i.e., red, yellow and blues. This led subsequent investigators to inquire as to what spectrally might be considered primary or fundamental. The work of these investigators is summarized in Principles of Physical Optics, Mach, Ernest, Dover, 1926, pp. 103 and more recently in Color--A Survey in Words and Pictures, Birren, Faber, University Press, 1963.
In general, the direction for modern theories was given by Thomas Young who assumed that the color response of the human eye was arbitrarily limited by two extremes at each end of the spectrum; i.e., red and violet, and that the mid section or green could be used as a minimum factor from which all other colors including white could be obtained, where white itself was assumed to be a combination of all three colors. Without further reviewing all of the arguments by the many investigators on the subject of what constitutes primary colors, it is sufficient to state that the three component theory of Young as modified by Helmholtz and experimentally corroborated by Maxwell, is accepted as the basis for a primary system consisting of red, green and blue. Added and superimposed upon this basic concept are the works of subsequent investigators in colorimetry who have added white and black as fundamental factors. However, mention should be made of further investigators who have taken the position that the human eye does not need to accept any combination of colors as primary since it may be demonstrated that any combination of opposite or complementary colors plus a third which may be derived from these two plus white will give a complete gamut of colors.
2. Prior Art
It will therefore be seen that many authorities have offered different theories of color and reasons why certain colors are to be considered primary or fundamental. However, few have challenged the method and procedures for examining colors in the visible spectrum as first proposed by Newton, that is, the use of a narrow slit in combination with diffraction means such as a grating or a dispersion means such as a prism.
One of the few investigators to challenge the basic tenets of color science was August Kirschmann. In a paper presented in 1917, Das Umgekehrte Spektrum Seine Komplementarverhaltnisse, Physikalisch Z. 18.195, Kirschmann indicated that color science would have developed quite differently if a small obstacle had replaced Newton's slit since the use of such an obstacle in combination with a prism will produce an inverted spectrum.
According to Ernest Mach, Helmholtz did utilize a wide slit in his efforts to disprove the red, yellow and blue primary color theory of David Brewster. Helmholtz contended that yellow and blue were the primary colors and that the white light formed between the spectral pairs utilizing a wide slit was white light comprising yellow and blue light.
In general, however, the narrow slit has been accepted as fundamental to the study of colors. The use of the narrow slit in present day spectral analysis equipment is well documented in the patent prior art. For example, U.S. Pat. No. 3,247,758 -- Turner discloses the use of narrow slits in a dual monochrometer system.